It is known that one may prepare methine compounds from 2(5H)furanones containing cyano, p-nitrophenyl, p-cyanophenyl, optionally substituted carbamoyl and carboxylic acid ester groups (see, for example, U.S. Pat. No. 3,661,899 and U.S. Pat. No. 4,617,373). The methine compounds disclosed in these two patents have a high degree of volatility and have a tendency to sublime, exude and migrate from polymeric substrates colored with them. Also, when applied to polyester fabric as textile dyes from a finely divided state they have a tendency to be removed from the fabric via washing and are sensitive to changes in pH. U.S. Pat. No. 4,617,373 shows that the compounds can be copolymerized into polyester compositions to reduce the sublimation, migration, etc. by incorporating reactive groups, e.g. ester groups, into the colorants and adding the colorants prior to the polyester forming reaction. Compounds such as those of Examples 20, 125, 126, 147, 195, etc. have a reactive group present only on the aldehyde portion of the reactant and not on the 2(5H) furanone active methylene portion of the methine compound; in this fashion, these compounds are incorporated into the polyester polymer, but they do not provide the greatest degree of nonextractability and lowest level of toxicity hazard. This is believed to occur because the methine linkage may be destroyed, e.g. by exposure to light, leaving the 2(5H) furanone moiety unattached to the polymer and thus rendering it extractable (see Example 761). In contrast, when the furanone moiety contains a reactive ester group in the 3-position (see Example 22 of U.S. Pat. No. 4,617,373) this moiety may still be attached to the polymer even though the methine linkage might be destroyed. The presence of the ester groups, however, as compared to a 3-cyano group, results in a detrimental hypsochromic shift in the absorption maximum (shift to shorter wavelengths) and a lowering of the color value (extinction coefficient) (see Table 1). In contrast, the presence of the reactive ester group on the 3-heteroaryl 2 (5H) furanone compounds of the present invention does not cause such a significant hypsochromic shift and lowering of the extinction coefficient (see Table 1 below).